Process of improving paper formation using hydroxyethyl cellulose or microbiological polysaccharides



United States Patent 3,245,871 PROCESS OF IMPROVING PAPER FDRMATIQN USING HYDROXYETHYL CELLULOSE OR MI- CROBIOLOGICAL POLYSACCHARIDES Christen H. C. Yang, Castro Valley, Calili, asslgnor to Crown Zellerhach Corporation, San Francisco, Calif a corporation of Nevada No Drawing. Filed Apr. 14, 1965, Ser. No. 447,950 5 (Ilaims. (Cl. 162177) This application is a continuation in part of application Serial No. 215,508 filed Aug. 8, 1962, now abandoned.

This invention relates to a process of making fibrous webs characterized by improved physical properties. More particularly, the invention pertains to a process of incorporating a chemical agent into an aqueous suspension of fibers to be used in the manufacture of a fibrous web, such as paper.

A highly desirable property of a finished fibrous web is its formation. As is Well known in the papermaking art, a good formation of a paper denotes a substantially uniform and homogeneous distribution of fibers within the body of the paper. The problem of a good formation in the paper manufacture is particularly significant when paper is to be made from fibers longer than normal papermaking fibers, as well as in the manufacture of light weight papers.

Many attempts have been made in the past to improve formation of paper in order to satisfy use requirements. Such attempts include incorporation into aqueous fibrous slurries of various natural gums, including deacetylated karaya gum, modified locust bean gum and guar gum; cellulose derivatives, such as sodium carboxyrnethyl cellulose, and other similar additives. Such materials, Which are characterized by a common property of being substantive to the fibers, are adsorbed or deposited on the fibers and retained in the fibrous web during its manufacture. Consequently, the white water which drains through the papermachine wire during the passage of the fibrous suspension thereover, is substantially free of such material and additional quantities thereof must continuously be added to the aqueous suspension of fibers to produce a web of uniform quality. While improvements in the formation of paper have been realized through treatment with some of the above mentioned materials, the use of such materials has been found not entirely satisfactory since they cause fiber sticking to the papermachine wire, clogging the wire, reduction of the drainage rate on the papermachine wire, and frequently increase of stiffness of the resulting paper.

The present invention has as a principal object an improved process of making a fibrous web by incorporating into an aqueous suspension of fibers a particular chemical agent which is substantially nonsubstantive to such fibers and is characterized by being capable of increasing the viscosity of Water.

,Another object of this invention is to provide a process of manufacturing paper characterized by an improved formation whereby many of the disadvantages inherent in prior art processes enumerated hereinabove are avoided.

Still another object of this invention is to provide a process of improving formation of a fibrous web through addition of a particular chemical agent to a pulp slurry in such a manner that the agent is separated from the fibers, recovered and recycled in a closed system of paper manufacture.

Still further objects and advantages of the present invention will appear from the following description of the invention.

The present process of making fibrous webs having improved formation broadly comprises preparing an aqueous suspension of fibers, comprising a chemical agent which is substantially nonsubstantive to such fibers, the chemical agent being added in an amount sufficient to increase the viscosity of Water alone to a range of from 20 to 500 centipoises measured at 20 C., distributing the chemical agent substantially uniformly in the fibrous suspension, flowing the fibrous suspension containing the chemical agent incorporated therein onto a papermachine wire to form a fibrous web while at the same time separating from the fibers the water containing a major por tion of the chemical agent, and drying the fibrous Web in the drying section of the papermachine.

Accordingly, the invention is based on the discovery that it is possible to produce a fibrous web, such as paper, characterized by a marked improvement in its formation by adding a specific chemical agent into an aqueous system containing fibers under such conditions that the chemical agent will not be deposited or adsorbed or otherwise retained on the individual fibers, and yet such fibers will be substantially uniformly distributed in the body of water prior to being directed onto the papermachine wire to give a fibrous web characterized by an excellent formation and being substantially devoid of the chemical agent incorporated in the system during the manufacture of the fibrous Web. Thus the white water which drains through the Wire contains the chemical agent in a substantially the same concentration as originally added to the fibrous suspension, so that by recycling the White Water further addition of the chemical agent is, in most instances, unnecessary.

As mentitoned hereinabove, the chemical agents which are employed in accordance with this invention are characterized by being nonsubstantive to fibers. In other words, such agents will not be adsorbed by the fibers or otherwise interacted with the fibers prior or during the formation of the fibrous web. Furthermore such agents are capable of increasing viscosity of the water. Moreover, aqueous solutions or dispersions of such chemical agents will not gel upon standing at room temperature during prolonged periods of time.

The chemical agents suitable in the practice of this invention comprise water-soluble hydroxyethyl cellulose, and high-molecular weight microbiological polysaccharides, particularly those derived from glucose.

Hydroxyethyl cellulose is the common designation for l-hydroxyethyl ether of cellulose. For suitability in the present process there should be sufilcient hydroxyethyl substitutions to impart Water solubility. An average of at least 1.7, and desirably more than 2.35 hydroXyethyl groups per glucose unit are present and the cellulose molecules desirably have an average molecular weight of between about 40,000 and 210,000. Intermediate molecular weight ranges such as around 150,000 have been found particularly suitable.

Suitable microbiological polysaccharides are those produced by microbial fermentation of glucose sugar with the bacterium Xanthomonas; especially the species Xanthomonas campestris and Xanthomonas phaseali. These polysaccharides may be suitably produced by fermentation in dilute aqueous sugar solution in the presence of common microbiological media to support growth, such as organic nitrogen sources (e.g., corn steep liquor) and potassium phosphate. These polysaccharides, having a molecular Weight in the order of millions, are linear polymers having an acid-stable, beta-linked backbone containing D-glucose, D-mannose and D-glucuronic acid constituents. For further information on these microbiallyproduced polysaccharides and their production, refer to US. Patent No. 3,000,790 and the following articles and the literature cited in these articles:

(1) Information on Polysaccharide B-1459, Northern Utilization Research and Development Division, US.

Department of Agriculture, Peoria, Illinois, #CA-N-9, September 1959.

(2) New Polysaccharide Gums Produced by Microbial Synthesis, Manufacturing Chemist, May 1960. (3) Exocellulose Bacterial Polysaccharide from Xanthomonas Campestris NRRL 13-1459, Canadian Journal of Chemistry, vol. 40, 1962.

The polysaccharides may be used in their natural form or they may first be deacetylated by a short treatment with dilute alkali at room temperature with exclusion of oxygen.

A wide variety of natural and man-made fibers may be employed in the process of this invention. The natural fibers may be derived from softwoods, hardwoods, and annual plants, such as bagasee and straws; such fibers may be produced by any of the conventional pulping processes. The man-made fibers include orlon, rayon, dacron, nylon and the like. These may be employed either singly or in admixture with each other.

Any of the aforesaid chemical agents may be admixed with an aqeuous suspension of fibers prior to the mechanical treatment of fibers by the conventional beating or refining equipment. Also, if desired, such chemical agents may be incorporated into the fibrous slurry after the beating or refining has been substantially completed but before the fibrous suspension is directed onto the paper-machine wire. It is important, however, that the chemical agent be substantially uniformly distributed in the fibrous slurry at the papermaking consistency by any suitable mixing or agitating means. A satisfactory method of adding the chemical agent to a fibrous slurry in a continuous papermaking operation is to prepare an aqueous solution of the agent having the desired viscosity value, adding the fibrous material thereto, running the resulting fibrous slurry onto a paper machine, and recycling the white water containing the chemical agent to a tank containing a new quantity of the fibrous slurry.

It will be appreciated that the amount of the chemical agent added to the aqueous fibrous suspension in accordance with this invention may vary depending upon the type of fibers employed in the manufacture of the fibrous web. Generally, the amount of the chemical agent added to the fibrous suspension should be suflicient to increase the viscosity of water alone to a value of to 500 centipoises, preferably from to 100 centipoises measured at 20 C. Usually an amount of from about 0.01 to about 0.2% of the chemical agent by weight of the water containing fibers in suspension will produce satisfactory improvement in the formation of the resulting fibrous web.

If desired, other materials conventionally employed as pulp additives may also be incorporated into the fibrous suspension. Such materials may include wet-strength resins, rosin size, acidifying agents, such as alum, starches and colorants frequently employed in the paper manufacture. It will be understood, however, that such pulp additives must be compatible with the chemical agent of this invention so that such agent will remain unaltered during formation of the web.

The pH of the fibrous suspension is not critical in using either hydroxyethyl cellulose or the polysaccharide, and this is a particularly advantageous feature of these agents. Thus any pH level between about 2 and 10 is satisfactory and the choice of pH will depend primarily on such factors as the character of the fibers and the presence or absence of wet-strength resins or colorants. Solutions of hydroxyethyl cellulose are clear and their viscosity depends upon the consentration and the viscosity grade of the material.

In carrying out the process of this invention, an aqueous fibrous suspension into which the selected chemical agent has been incorporated and substantially uniformly distributed is run onto the paper-machine wire at a usual papermaking consistency in the neighborhood of 0.5%. The preponderant proportion of water containing the chemical agent originally incorporated is separated from the fibers during the formation of the web and flows freely into a collecting tray located under the wire from which it may be recovered and recycled for reuse in treating subsequent quantities of fibrous suspensions. Thus, it is one of the important features of this invention that white water derived from the wet section of the paper machine contains nearly the same concentration of the chemical agent as the original fibrous suspension and may be reused in a closed papermaking system. In this manner, addition of new quantities of the chemical agent is in most instances unnecessary or at the most limited to an insignificant quantity merely to compensate for small mechanical losses thereof or its dilution due to addition of fresh water, such as shower water, during the manufacture of fibrous web. After the fibrous web has been formed, it is passed through the drying section of the paper machine and wound up on a reel in the usual manner. The resulting dried fibrous web is substantially devoid of the chemical agent incorporated into the system during its manufacture.

The herein described invention will further be illustrated by means of the following examples which are intended to be descriptive of the invention in preferred embodiments thereof, percentages being expressed by weight and viscosity values being obtained upon measurements with a Brookfield viscometer at room temperature using spindle No. 3 at 20 revolutions per minute.

Example 1 An aqueous solution of hydroxyethyl cellulose was prepared by dissolving in a conventional beater 16.7 lbs. of commercial water-soluble hydroxyethyl cellulose having an average molecular weight between 150,000 and 210,- 000 and approximately 2.5 hydroxyethyl groups per glucose unit, marketed by Hercules Powder Co. under the trademark Natrosol HR 250, 2,000 gallons of water, resulting in an 0.1% solution of hydroxyethyl cellulose having a viscosity of about 25 centipoises. To the resulting clear soltuion there was added 167 lbs. oven-dry basis, of semi bleached softwood kraft pulp, which was beaten to about 380 cc. Canadian Standard Freeness. The consistency of the resulting fibrous slurry was 1% and its pH was 4.5. After the fibrous slurry was mixed to distribute the hydroxyethyl cellulose agent substantially uniformly, it was diluted with fresh water to 0.5% consistency in the papermachine headbox and run onto a Fourdrinier papermachine wire to form a fibrous web while the water containing the hydroxyethyl cellulose was drained through the wire and recovered for further use. The paper as it came off the drying section of the paper machine was tested for formation in the formation tester, supplied by the Thwing Albert Instrument Company, Philadelphia, Pennsylvania. For comparison, control paper also was made from the same pulp without hydroxyethyl cellulose having been added thereto. The following table indicates the values obtained on the untreated control paper and the hydroxyethyl cellulose-treated paper. It will be noted that the higher the value, the better is the formation of the paper.

Formation:

Control paper 64 Treated paper Thus the treatment of papermaking fibers with watersoluble hydroxyethyl cellulose, markedly improved the formation of the resulting paper as compared to the untreated paper. Moreover, the papermachine operation using the treated fibrous suspension was highly satisfactory as indicated by no clogging on the wire. Also, the treated paper had a lower stiffness as compared to the untreated control paper.

Example 2 In a manner essentially similar to that described in Example 1, 34 lbs. of the same water-soluble hydroxyethyl cellulose as described in Example 1 was incorporated into a fibrous suspension prepared by admixing 42 lbs. of rayon fiber of 1.5 denier and fli-inch length and 125 lbs. of alpha-cellulose sulfite pulp in 2,000 gallons of water, corresponding to about 1% pulp consistency. The amount of the hydroxyethyl cellulose incorporated was sufiicient to increase the viscosity of the water alone to 35 centipoises. The formation tests carried out in the same manner as in Example 1 on the resulting paper and on the untreated control paper gave the following results:

Formation:

Control paper Less than 50 Treated paper 100 The values below 50 are immeasurable and indicate a verp poor formation of the tested paper.

Example 3 Formation:

Control paper Less than 50 Treated paper 86 Example 4 Paper was prepared by adding the same hydroxyethyl cellulose as described in Example 1 to an aqueous suspension of bleached softwood sulfite pulp at 0.5% consistency in an amount suificient to increase the viscosity of the Water alone to 50 centipoises. The resulting paper had a markedly improved formation as compared to a paper prepared from the same pulp without the addition of the hydroxyethyl cellulose. The results were as follows:

Formation:

Control paper Less than 50 Treated paper 100 Example 5 The procedure of Example 4 was repeated using bleached cottonwood kraft instead of bleached sulfite. The results are given hereinbelow:

Formation:

Control paper 55 Treated paper 135 Example 6 The procedure of Example 4 was again repeated using bleached bagasse kraft pulp as the fibrous raw material. The results of the tests were as follows:

Formation:

Control paper Less than 50 Treated paper 115 Example 7 The procedure of Example 4 was again followed using a fibrous furnish consisting of 80% softwood groundwood and 20% softwood sulfite pulp. The test results were as follows:

Formation:

Control paper 60 Treated paper 125 Example 8 The procedure of Example 4 was again repeated using, as a chemical agent, Polysaccharide B-l459, a high molecular weight microbiological polysaccharide derived from glucose by fermentation with Xanthomonas campestris and containing mannose, glucose and a glucuronate salt in the approximate molar ratio of 2:1:1, respectively. The compound contained 1 acetyl group for every 4 sugar units.

The formation tests carried out in the same manner as described hereinabove gave the following results:

Formation:

Control paper Less than 50 Treated paper Accordingly, it is apparent that by the present invention I have provided an improved process for the manufacture of fibrous webs, such as paper, which process includes addition into an aqueous suspension of fibers of a specific chemical agent which is characterized by being substantially nonsubstantive to the fibers, capable of increasing viscosity of water, and stable over a wide pH range and in the presence of ionic salts. Through interaction between the water containing the chemical agent and the fibers suspended therein, a significant improvement in the formation of the resulting fibrous web results. Moreover, the conventional papermaking operations at the wet end of the paper machine are materially improved due to the presence of such chemical agent in the aqueous fibrous slurry. Due to a marked effect of the chemical agent on the rearrangement and distribution of fibers in the aqueous suspension, it is possible to employ longer fibers than normally employed in papermaking operations while still producing a sheet having an excellent formation. Also, it is possible to increase the pulp consistency in the headbox thus rendering the papermaking operation easier and more economical due to smaller volume of water removed from the fibrous suspension during formation of the fibrous web. It is also significant from the operational and economical standpoint that the preponderant proportion of the chemical agent admixed with the pulp slurry is separated from the fibers during the formation of the web and may be recycled and reused in a closed paperrnaking system.

It is to be understood that various modifications and changes may be made in the hereinabove described process and materials within the scope of the invention as defined in the appended claims.

For example, it is quite advantageous and a material part of this invention to recycle the agent-containing water collected from the paper machine wire in undiluted form (i.e., without adding to it the wash water normally collected with it in the recycle system of a paper machine) since this will eventually lead to waste of the oversupply of recirculated water and thus waste of a portion of the agent discarded therewith. Nevertheless, the agentcontaining water may be so diluted and make-up quantity of agent added to replace the lost agent.

I claim:

1. A continuous process for making a fibrous web of improved formation which comprises forming an aqueous slurry of fibers, said fibers being selected from the group consisting of cellulosic fibers and synthetic resin fibers, and said slurry containing a substantially nongelling water viscosity increasing agent which is substantially nonsubstantive to said fibers in the amount sufficient to increase the viscosity of water alone to a range of from 20 to 500 centipoises, measured at 20 C., said agent being selected from the group consisting of water-soluble hydroxyethyl cellulose having an average molecular weight of between about 40,000 and 210,000 and an average of more than 2.35 hydroxyethyl groups per glucose unit and microbiological polysaccharides produced by microbial fermentation of glucose with a bacterium of the genus Xanthomonas, flowing said slurry onto a paper machine to form thereon a web from said fibers while separating and recovering from said fibers the agent-containing water, in substantially undiluted condition, continuously recycling a major portion of said agent-containing water in substantially undiluted condition to form, with more fibers, additional slurry for flowing onto the paper machine, whereby said agent may be continuously reutilized and loss thereof through dilution minimized.

2. The process of claim 1 wherein the viscosity of water alone is increased to a range of 25 to 100 centipoises measured at 20 C.

3. A process of improving formation of a fibrous web which comprises preparing an aqueous suspension of fibers containing a substantially nongelling water viscosity increasing agent which is substantially nonsubstantive to said fibers in an amount sufficient to increase the viscosity of water alone to a range of from 20 to 500 centipoises, measured at 20 C., said agent comprising microbiological polysaccharides produced by microbial fermentation of glucose with the bacterium Xanthomonas campestris, flowing the suspension onto a paper machine to form thereon a web from said fibers while separating from said fibers water containing a major portion of said agent, and drying the web.

4. A process as in claim 3, wherein said agent-containing water is containuously recovered and recycled in substantially undiluted condition to form, with more fibers, additional slurry for flowing onto the paper machine, whereby said agent may be continuously reutilized and loss thereof through dilution minimized.

5. A continuous process for making a fibrous web of improved formation which comprises forming an aqueous slurry of fibers of paper making consistency, said fibers being selected from the group consisting of cellulose, rayon, polyester, acrylic and nylon fibers, and said slurry containing a substantially nongelling water viscosity increasing agent which is substantially nonsubstantive to said fibers in an amount between about 0.1% and 0.2% by weight of water, said agent being selected from the group consisting of water-soluble hydroxyethyl cellulose having an average molecular weight of between about 40,000 and 210,000 and an average of more than 2.35 hydroxyethyl groups per glucose unit and microbiological polysaccharides produced by microbial fermentation of glucose with the bacterium Xanthomonas campeslrl's, flowing said slurry onto a paper machine to form thereon a web from said fibers while separating and recovering from said fibers the agent-containing water, in substantially undiluted condition to form, with more fibers, additional slurry for flowing on the paper machine, whereby said agent may be continuously reutilized and loss thereof through dilution minimized.

References Cited by the Examiner UNITED STATES PATENTS 3,093,534 6/1963 Filling 162-168 OTHER REFERENCES Miskel: Surface Activity and Its Application to DONALL H. SYLVESTER, Primary Examiner.

S. LEON BASHORE, Examiner. 

1. A CONTINUOUS PROCESS FOR MAKING A FIBROUS WEB OF IMPROVED FORMATION WHICH COMPRISES FORMING AN AQUEOUS SLURRY OF FIBERS, SAID FIBERS BEING SELECTED FROM THE GROUP CONSISTING OF CELLULOSIC FIBERS AD SYNTETIC RESIN FIBERS, AND SAID SLURRY CONTAINING A SUBSTANTIALLY NONGELLING WATER VISCOSITY INCREASING AGENT WHICH IS SUBSTANTIALLY NONSUBSTANTIVE TO SAID FIBERS IN THE AMOUNT SUFFICIENT TO INCREASE THE VISCOSITY OF WATER ALONE TO A RANGE OF FROM 20 TO 500 CENTIPOISES, MEASURED AT 20*C., SAID AGENT BEING SELECTED FROM THE GROUP CONSISTING OF WATER-SOLUBLE HYDROXYETHYL CELLULOSE HAVING AN AVERAGE MOLECULAR WEIGHT OF BETWEEN ABOUT 40,000 AND 210,000 AND AN AVERAGE OF MORE THAN 2.35 HYDROXYETHYL GROUPS PER GLUCOSE UNIT AND MICROBIOLOGICAL POLYSACCHARIDES PRODUCED BY MICROBIAL FERMENTATION OF GLUCOSE WITH A BACTERIUM OF THE GENUS XANTHOMONAS, FLOWING SAID SLURRY ONTO A PAPER MACHINE TO FORM THEREON A WEB FROM SAID FIBERS WHILE SEPARATING AND RECOVERING FROM SAID FIBERS THE AGENT-CONTAINING WATER, IN SUBSTANTIALLY UNDILUTED CONDITION, CONTINUOUSLY RECYCLING A MAJOR PORTION OF SAID AGENT-CONTAINING WATER IN SUBSTANTIALLY UNDILUTED CONDITION TO FORM, WITH MORE FIBERS, ADDITIONAL SLURRY FOR FLOWING ONTO THE PAPER MACHINE, WHEREBY SAID AGENT MAY E CONTINUOUSLY REUTILIZED AND LOSS THEREOF THROUGH DILUTION MINIMIZED. 